Method and device for after-treatment of exhaust gas

Abstract

A method and a device for use in the aftertreatment of exhaust gas of an internal combustion engine, in particular of a diesel engine, are described, having a device for providing oxidizing agents and an exhaust-gas aftertreatment unit, a temperature sensor ( 40 ) being provided to measure the temperature of the exhaust gas before it enters the exhaust-gas aftertreatment unit ( 10 ) and the device ( 20 ) for providing oxidizing agents being set up to vary the chemical composition of the oxidizing agents as a function of the temperature. This method of exhaust-gas aftertreatment ensures energy-efficient preparation of the exhaust gas.

What is claimed is:  
     
         1 . A method for use in the aftertreatment of the exhaust gas of an internal combustion engine, in particular of a diesel engine, in which oxidizing agents are produced at least intermittently in a first step and the exhaust gas undergo aftertreatment in a further step, wherein the temperature of the exhaust gas is determined before the aftertreatment, and the chemical composition of the oxidizing agents is varied as a function of the temperature ( 150 ).  
     
     
         2 . The method as recited in  claim 1 , 
 wherein ozone and/or nitrogen dioxide are used as oxidizing agents.    
     
     
         3 . The method as recited in one of the preceding claims, 
 wherein the oxidizing agents are obtained from the exhaust gas.    
     
     
         4 . The method as recited in  claim 2  or  3 , 
 wherein mainly ozone is produced below a temperature threshold value.  
 
     
     
         5 . The method as recited in one of the preceding claims, 
 wherein the oxidizing agents are generated in a plasma.    
     
     
         6 . The method as recited in  claim 5 , 
 wherein a non-thermal plasma is used as the plasma.    
     
     
         7 . The method as recited in one of the preceding claims, 
 wherein the aftertreatment includes removal of soot particles and/or oxidation of hydrocarbons.    
     
     
         8 . The method as recited in claims  4  and  7 , 
 wherein the temperature threshold value is approximately 200 degrees Celsius.  
 
     
     
         9 . The method as recited in  claim 7  or  8 , 
 wherein a particle filter is used, the degree of filling of the particle filter is determined, and the oxidizing agents are provided as a function of the degree of filling in order to intermittently initiate combustion of the soot particles accumulated in the particle filter.  
 
     
     
         10 . A device for use in the aftertreatment of the exhaust gas of an internal combustion engine, in particular of a diesel engine, having a device for providing oxidizing agents and an exhaust-gas aftertreatment unit, 
 wherein means for determining the temperature of the exhaust gas before it enters the exhaust-gas aftertreatment unit ( 10 ), in particular a temperature sensor for measuring the temperature, are provided; and the device ( 20 ) for providing oxidizing agents is set up to vary the chemical composition of the oxidizing agents as a function of the temperature.